Question

Antimony - Bismuth thermocouple generates a thermo emf of $100\mu V{/}^{0}C$ When the cold junction is at $0^{0}C$ . A micro ammeter of resistance 100 $\Omega$ is connected in the circuit of Sb - Bi thermocouple. If the least count of the micro ammeter is $1\mu A$. The minimum temperature difference it can measure is (Neglect the resistance of Sb - Bi thermocouple.)

• A. $1^{0}C$
• B. $2^{0}C$
• C. $3^{0}C$
• D. $4^{0}C$

Answer 1

Answer: (A)

$1^{0}C$

The minimum voltage that should be generated by thermocouple so that ammeter senses the change in current is

$V=0.1\mu A\times 100\Omega =100\mu V$

so minimum temperature difference across thermocouple should be $\Delta T=100\mu V/100\mu V{}^o{C}^{-1}=1{}^{o}C$